Microcrystalline wax compositions



Y 2,841,367 MICROCRYSTALLINE WAX COMPOSITIONS John W. Walsh, Crystal Lake, and Weldon Grant Annable, Mundelein, 111., assignors to The Pure Oil Company, Chicago,.lll., a corporation of Ohio No Drawing. Application October- 29 1954 Y Serial No. 465,736 g '4Claims. or. 196-449 This invention relates to a microcrystalline wax composition. More particularly, it relates to a microcrystalline wax composition having superior low-temperature characteristics, rendering it especially suitable as a widerange laminating and coating composition.

Microcrystalline waxes are those waxes which have a finer, less apparent crystalline structure than parafiin wax and which comprise a solid hydrocarbon mixture of molecular weight averaging higher than parafiin wax. Microcrystalline waxes possess plastic properties and are obtainable from crude petroleum fractions commonly designated as heavy lubricating and cylinder oil stocks. Petrolatum wax is the term applied to microcrystalline wax refined from heavy etrolatum stock; and is usually of a sticky nature with about l55-165 F. melting point and penetration-value of more than about 25. Crude petrolatum wax contains as much as 30 percent oil; the oil content maybe reduced considerably by a number of processes,'for example, reprecipitation of the fraction from naphtha or by pressing. Microcrystalline waxes containing a smaller-amount of oil than petrolatum wax are generally of higher melting point, that is, 170 to 195 F., and in some cases up to 200 F. melting point. All microcrystalline waxes are of about the same molecular weight and are said to be' composed of hydrocarbon chains of twice the length of those of the'macrocrystalline waxes. The cause of the small size of the crystalline structure is not definitely known but, according to some authorities, has been attributed to the presence of an unsaturated hydrocarbon. The presence of oil apparently has the effect of furtherinhibiting macrocrystallizae tion.

Microcrystalline waxes because 'of their plasticity and other suitable characteristics, including in general'a relatively high melting point, have found extensive commercial use. Microcrystalline waxes have been utilized to advantage as adhesives or binding agents for laminating plies of-various substances, usually paper, as in the preparation of field-ration packages and food wrappers and as greaseand Water-proof coatings on-meat and fruit, milk bottles, cardboard cartons and the like. These waxes have found application for the same general purposes as paraffin waxes.

2 p general, however, they have been more satisfactory than parafiin waxes which exhibit greater brittleness under such low temperature conditions. foods which are frozen and stored at low temperatures,- all types of waxes which have been utilized heretofore have proved to be unsatisfactory per se. Resort has had' to be made to the compounding of the most suitable type of waxes, namely, the microcrystalline waxes, with foreign materials to modify the insufiicient flexibility-at; low temperatures such as 10 F. Frequently, the foreign materials have been found to be dilficult to blend with the wax, or expensive, or otherwise unsatisfactory. Foreign materials commonly used to increase low temperature flexibility have been rubber, resins, polymers and the like.

A compounded microcrystalline wax has been sought which would afford good coating characteristics at low (down to 10 F.) temperatures as well as at room or normal temperatures, that is, would not scuff or peel, would be adhesive to papers and the like, yet'not be tacky to the touch and would remain flexible. A laminating wax would require similar flexibility, plus a pleasant odor and good bonding properties. In order to achieve such goals in a single, multi-purpose wax, microcrystalline wax prepared by special techniques has been blended with mineral oil to produce a low-temperature, laminating composition. However, such microcrystalline wax has been of a hard nature, with a melting point substantially above 180 F. and a viscosity of about 120 seconds or more SUS 210 F. This blended wax exhibits superior high-temperature laminating characteristics, but at room temperature (65 -80 F.) would be excessively tacky or sticky and inferior when compounded with a suflicient amount of oil to render it suitable as a normal and lowtemperature coating composition. 7

Accordingly, it is an object of our invention to provide a superior laminating and coating 'wax. It is another object of our invention to provide a superiorpetroleum I hydrocarbon microcrystalline wax composition which is Because, of their adhesiveness and plasticity over fairly wide temperautre ranges, microcrystalline waxes have been used'particularly in the field of coating of paper and similar substances. Microcrystalline waxes which'have been used at relatively low temperatures as surface coatings, and also as laminating'agents in the preparation of multiply pap'enhave not been completely satisfactory because,ofwtheirmbrittleness and lack of pliability. In:

flexible and adherent to paper and other fibrous ma terials at low and ordinary temperatures, and is especially suitable both as a coating composition and as a laminating composition for use over a wide temperature range, extending to at least 10 F. Other objects, advantages and uses of'our invention are apparent from this specification and accompanying claims. I

It has been discovered that microcrystalline wax can be suitably modified by the addition thereto of a critical amount of a petroleum hydrocarbon oil fraction which In the packaging of' rendersit sufliciently flexible at low and freezing temperatures and sufficiently adhesive to paper and the; like materials to be bonded to multi-plypaper and to furnish other superior coating and laminating properties. Both the coating characteristics and the laminating'properties of our microcrystalline wax'composition remain suitable for commercial use overa wide temperature range, in-' cluding temperatures as low as 10 F. or below. Indiscriminate addition of hydrocarbon oil to the microcrystalline'wax cannot achieve similar results.'. A limited" range of 'oil' concentration has been found within which the oil.

satisfactory characteristics are imparted to the wax by I Microcrystalline waxes used as the bases"in the"com= position of our invention have the following general char acteristicsz' TABLE I Melting point, F Below 180 F. and above about 165 F. Penetration at 77 F Above 15. Viscosity SUS 210 F Below 90. Stain test Does not pass at 120 F.

The microcrystalline wax of our invention may be obtained from a Van Zandt crude or from other petroleum sources. In the process of refining, the Van Zandt or other crude oil is divided into, a number of fractions including a fraction from which lubricating oils. are ultimatelyderived. This fraction isfurther fractionated by the use of steam and/or vacuum into neutral fractions of various viscosities, and residuum. From said residuum,the microcrystalline wax may be derived.

During; the process of separation of microcrystalline wax, the cylinder stock is subjected to normal dewaxing and deoiling procedures to. produce the finished wax of the characteristics above noted in Table I. Dewaxing may be performed by any one of a number of suitable processes, including solvent extraction and low-temperatu re crystallization, followed byseparation. by centrifugation, Solvent'dewaxing may employ any one of a number of suitable solvents or solvent mixtures, or solventanti-solvent mixtures, but preferably utilizes a mixture of methyl ethyl ketone and toluene in a ratio of solvent mixture-to-oil of'about 1:1 to 4:1, depending upon the nature and viscosity of the charge stock. In a typical operation, after suitable contact of solvent with the oil fraction, rich solvent containing dissolved wax is separated from the oil by a suitable means, such as a settlingtank or the like, after which the solvent is removed from the wax'by the application of heat and/or reduced pressure, and the wax is obtained in relatively pure, solid form. The characteristics of the microcrystalline wax at this stage in the processing somewhat depend upon the concentration of oil entrained therein.

Generally, wax is obtained with a relatively large oil content so that the wax has a low melting point and is tacky. This wax is therefore of the petrolatum. type. The oil: content of the microcrystalline wax is. further decreased to about 0.7 percent for a. commercially-used, microcrystalline wax of characteristics as given in Table I above, by any one of a. number of deoiling methods, suchas pressingto squeeze the oil out or by the application of heat and/ or reduc d pressure. Preferably, a second solvent extraction may be performed at conditions similar to those of the dewaxing step except for higher temperatures. The Wax may be precipitated from the solvent solution by chilling'and' be removed by centrifugation; or, the solution containing. the wax may be filtered to remove. solventand oil therefrom to produce purified, deoiled lmicrocrystalline Wax.

Followingthe .dewaxing and deoiling procedure, which may be carried out in conventional apparatus, the substantially oil-free microcrystalline wax, containing only about-0.7 percent of retained oil, maybe subjected to a bleaching process, if desired. The bleaching process. may incorporate fullers earth, an earthy, fine-grain form of-clay, essentially calcium montmorillonite. The fullers earth isutilized in a percolation or contact operation, For-apercolation process, tanks 5 to feet in diameter and 20 to 30 feet'high are used in which the fullersearth ofgranular (30 to 60 mesh) form is-placed and through whichthe. wax which has been heated to a liquid form is run. In a contact-process, fine fullers earth, etc., are mixed to an extent of about 10 percent with hot, moltenwaxvin a large vat, and further heated to a temperature about 20 percent above the wax fusion point, after which thewax-is squeezed from the clay in a filter press.

The hydrocarbon oil fraction which may be used as theadditive in the preparation of thecomposit-ion of ourinvention to improve the beneficial, low-temperature characteristics of the microcrystalline wax may-hearty;

lubricating oil raction,v such. as, 17.0 SUS. (at..2l0, E). viscosity bright stock, or an aromatic extract from a lubricating oil base stock, such as that obtained by phenol extraction. Soft waxes are unsatisfactory fractions for this purpose and should not be used. Soft waxes are those of low melting point (approximately -l25 F.) which contain variable-amounts of oil and are separated during the preparation of microcrystalline waxes.

As stated above, in general our invention comprises a microcrystalline wax composition with superior laminating and coating characteristics. In particular, our invention comprises a microcrystalline wax composition incorporating a petroleum lubricating oil fraction in a critical amount which is especially effective in low-temperature use of the composition, such as in the coating and laminating of meat wrappers-and other papers-utilized as coverings for perishables storedatlow temperatures. A particular point of novelty of our invention comprises the discovery of a critical concentration, ofa petroleum lubricating oil fraction ,to. obtain greater flexibility in the wax, as well as increased laminating, strength, at temperatures as low as 10 F. without tackiness at any ambient temperatures. Stickiness or tackiness cannot be tolerated in a coatin wax, that is, the coating wax must be adhesive in order to closelyadhere to the surface, but it cannot be tacky.

or softtothe touch. The coating, for example, of a paper carton must be closely adherent to thepaper surface but one must be able to handle the coated container without marring or removing the coating; A superior coating- Wax must also have flexibility-inorder to resist chipping,

cracking and peeling when the coated surface is-subjected to bending'stress.

A laminating wax must also have enough adhesiveness to' closely adhere to'the surface to be treated, for example; sufiicient to bond together two plies of a'substancesuch" as paper and must remain pliable at any temperatures to which the wax-bonded material normally may-be exposed.

Moreover; asatisfactory laminating'waxmust also'havea high: degree of laminating strength over a wide temperature range so that the laminated plieswill not-be pulled apart or peel under normal conditions of use:

To. be commercially desirable, bothlaminating wax I and'coatingiwax'should have a suitable odor, especially since many current uses place such waxes in contact with or near edibles.

The microcrystalline: wax composition of our invention was experimentally-compared with three other waxes,-

wax A, wax B and wax- C, said waxes being commercial laminating preparations of;microcrystalline wax'. The-results. are recorded below in Table .II:

TABLEII (1)- light microcrystalline wax (wax of. characteristics of Table I), 5% special Oil W (bright The odor test was conducted in the'foll'owing-manner:

A 50 ml. beaker is half filled with di'stilledwater and is heatedto the -boiling pointx' Two to three grams' of the waxv'to be evaluated'are placed in the' hot water so that thewax when melted'formsa liquid layer approximately 1 The contents of thebeaker are swirledandj the vapors are sniffed to de- Odors rangeas follows: odorless,-. slight, moderate; objectionablex Ratr ings are; assigned in thisorder onaznumerieal :sc'ale rang--- thick on the surface of. the water.

termine if rthe -1wax possesses an. odor;

5 ing from 1 to 4. The lower the odor number, the more satisfactory the odor.

The aboveltableindicates that the compounded wax composition of our invention, i. e., (1), (2), and (3) had odors comparable with commercial laminating wax C and better than those of commercial laminating waxes A and B. The composition of our invention is therefore at least as suitable in odor as current, commercial laminating waxes and is better than some laminating waxes in that respect.

Table IIIexhibits the low-temperature flexibility of a number ofrnicrocrystalline wax compositions, namely, those containing the microcrystalline wax utilized as the base in the composition of our invention, together with a variety of higher-boiling petroleum fractions. The lowtemperature flexibility test was performed in the following manner: The waxes to be tested for low-temperature flexibility are prepared by coating a film of the wax approximately /t;,. thick on the surface of hot water in a flat glass dish such as a Petri dish. The wax is permitted to solidify, and is then cut into strips measuring 1" x 3" x Va"; These test strips of wax are placed in a refrigerator'maintainedat 10 F. for 1 hour. The conditioned strips are then placed in a slot of the testing device which holds one end of the wax strip rigid while the other end may be bent back and forth through 180". The test is run in the refrigerator at -l F. and the flexibility is evaluated as follows. 0 bends (if strip is brittle and breaks before going through 90) to 30+ bends. 'Tests are run on five strips and the number of bends are averagedasan indication of low-temperature flexibility.

TABLE IH Low-temperature flexzbzlzty Composition Microcryst he Flexibility f I -Wax, Perat 10 F. Modifying Agent Perve ent cent W None O 100 None; brittle.

' 95 D0,. 90 Do. Petroleturn 85 Do. 75 Do. 42 I go. Soft Wax (from 85 viscosity m 90 0. neutral stock). 15 85 D0 5 95 Do. 10 90 Same; good for 170 viscosity neutral oil 5 bends.

, 15' 85 Good; good for bonds.

5 95 None; brittle. 160 viscosity bright stock 10 '90 Same; good for p 11 bands.

15 85 .Good; good for 30 bends.

Extract B l 85 Good; good for 3O bends. Extract N 9 17. 5 82. 5 Do.

1 Extract B is a commercial phenol extract obtained in making high viscosity index bright stock. 7

1 Extract N isa commercial phenol extract obtained in making high viscosity index neutral oil. V The microcrystalline wax is the wax described for Table I above.

In addition, "the laminating strength of various microcrystalline waxes, modified with varying quantities of higher-boiling hydrocarbon fractions was tested by the following procedure, the results of which appear in 1 The microcrystalline wax is the wax described for Table I above.

The results of the above tests indicate that the flexibility of microcrystalline wax of the type utilized as a base in the microcrystalline wax composition of our invention is especially suitable, that is, is sustained over a test period of more than 30 bends, when a lubricating oil fraction, such as viscosity neutral oil, or other fraction is utilized in a concentration of about 15 weight percent, based on the total weight of oil, with the microcrystalline wax. With the same modifying agent, less satisfactory results may also be obtained in most cases with only aboutlO weight percent of the modifying agent, that is, flexibility is sustained over a test period of about 5 bends. The 15 weight percent concentration is, of course, preferred. However, it should be noted that when the modifying agent, such as 170 viscosity neutral lube oil, is present in a lesser weight percentage, for example 5 weight percent, the flexibility of the wax-oil composition drops to 0 and the composition is too brittle at 10 F. to be satisfactory as a low-temperature, coating composition. Comparable results are obtained when other petroleum lubricating oil fractions are utilized in combination with the microcrystalline wax in comparable concentrations of 5-15 percent; thus, when Extract B was utilized in 15 Weight percent concentration, satisfactory flexibility was obtained, as was the case when Extract N was utilized in a slightly greater concentration of 17.5 weight percent. In the latter case, the coating ability and flexibility of the wax-oil composition was present with above 15 weight percent oil, but as has been noted heretofore, concentrations substantially greater than 15 weight percentimpart undesirable tackiness to the coating composition and render it unsuitable for use, even though the flexibility mayhave been increased. It is therefore shown that with respect to all of the coating characteristics of the microcrystalline wax composition of our invention, a critical range of total oil concentration is necessary, and when the oil concentration falls below about 15 weight percent the composition is more like unmodified wax, brittle at 10 F. and hence unsatisfactory for coating. While concentrations of 10 weight percent of the modifying agent produce flexible wax compositions, concentrations of about 15 weight percent produce greatly increased flexibility. Moreover, the optimum of about 15 percent by weight of modifying agent cannot be greatly exceeded Without deleteriously affecting the other desirable properties of the coating wax, rendering said wax too tacky for use at room or normal temperatures.

With regard to the laminating strength of the various microcrystalline wax-modifying agent compositions, Table IV above shows that a satisfactory laminating strength, calculated in grams per-inch is obtained when Extract B is blended with the microcrystalline wax in an amountof about 15 percent, said blend giving a value of 69; Extract N also registers a value of 69' when 17.5 weight percent is used in combinationwiththe:microcrystalline wax. A relatively high reading, -51, is attained when 15 percent 170 viscosity neutral lube oil is addedtozmicrocrystalline Wax, and a "slightly higher reading is attained when the same oil is added in 10 percent amount to the wax. A slightly lower, but still satisfactory reading of 50 is obtainpd when 15 weight percent of, 150 wviscosity bright stock is added to the wax. However, when weight percent of 170 viscosity neutral .oil or 11.50 viscosity bright stock is added, the laminating strength is somewhat lower than with percentages near the optimum.

The above results indicate that the'addition of -15 weight percent of a petroleum lubricating oil fraction to the wax increases its laminating'strengthto a highvalue; in the absence of such modifying agent the laminating strength of the base-wax is nil.

T bl V belo fu the il ustrates t influ n f il n e at onq tl rtflrt tttiflss- It -is-conc-luded from the above results that a critical range of concentration of about 10 to about weight percent of-petroleum hydrocarbon lubricating oil fraction modifying agent is necessary when theagent is utilized in combination withthe base microcrystalline wax to p roduce the desired laminatingstrength andilexibility of the final -wax composition and render it suitable for coating and laminating purposes over a wide temperature range extending down toabout 10"F. "When the modifying agent is added in an amount lessthanabout 10 weight percent of the composition, the laminating strength is lessened, and flexibility i usually nonexistent, ,making the wax composition unsatisfactory as a-dual-purpose coating and laminating agent fordow-temperatureuse. -When more than about 15 weight percent of the modifying agent is incorporated in the microcrystalline wax, undesirable stickiness and tackiness render the .rnicrocrystalline wax composition unsuitable as either a coating or laminating agent. Moreover, laminating strength decreases to a low value. A critical range of 10--15 weight percent of the o p fi yp .mqd f n agent's exis w h which desired coating and larninating characteristics are obtained, that is,in which thelarninating strengthis high, the low-temperatureflexibility is increased and the composition is essentially non-tacky.

The modifier may be added to the waxin any manner, that is, rapidly, slowly, intermittently, or continuously, with or without stirring, but in such a manner to produce a homogeneous wax composition with the modifier evenly distributed therein. i

A non-limiting'example of the composition of our invention appears below.

Example I Van Zandt crude oil is subjected to fractionation by distillation to produce a lubricating oil fraction. Said lubricating oil fraction .is subjected to vacuum distillation at about 750"F. and 100 1 20 mn1. Hg to produce distillate lubricating oil fractions and a residuum with the following characteristics:

yuan a t 7 The distillates and residuum are further processed to produce neutrals and brightsto'ck. The residuum 'is subjected to adewaxing procedure which co prisesmixing it at l50 F. and atmespneriapressnre with methyl ethyl-ketone and/or toluene in 'a proportion of 47 parts of methyl ethyl keto emsa" parts of toluene andin'a solvent-to-oil ratio of 4E1. The solvent oil mixture is then chilled down to temperatures of about F. to 14 F. during whicll timethe wax' ciystalli zesout of solution. The wax is" removed from the solutiorl"by filtration. i

Afterthe above dewaxing procedure,then icrocrystah line waxso isolated is s bib ted to aj'deoiling s tep which comprises remixing it with methylfe' f l c'e'tonejandlor toluene in the proportion of 47 parts methyl ethylketone to 53 parts toluene and in a ratio'of solventtol-oil of 8: 1 at temperatures of 140-l50 F. The solvent-wax mix ture is then chilled down to temperatures of 35-50" F. during which time the desired wax crystallizes out of solution. This ,wax is separated from 'the oil and soft Wax by filtration he Purifie d q q ini rl cr ellin wax containing only about 0.7 weight percent ofoiljhas' the following characteristics:

Melting point, F Penetration at 77 F- 15-20 Viscosity SUS at 210. F 87.9 Stain t Fail Flexibility at 10 F--- Brittle. -1-2 .i 30. Laminatingstrengthin 35 67 58.

grams per inch. dor a 4 3.5- 3. Consistency Not tacky- N'ottacky Nottackyslighltily ac y When applied to a paper surface, the coating and laminating wax adheres closely tosaid. surface,.remains flexible at temperatures as low as .l0 .F., :does'not present an objectionable odor or color, and does not chip, crack or peel from said surface. Moreover, said wax when applied between .two prepared sheets. of paper. passagcover a heated roller at 212 F. forms satisfactorily bonded paper plies and remains flexible even at, 10. F.

The hydrocarbon ,oil fraction in the composition of our invention which may be added to the microcrystalline wax includes any .petroleumiraction inj theglubricating oil range,..,ex clusive of petrolaturns or sirnila v .Thefinal composition of the crocrystalline waxmodifying agent combinationis intended not only as a. oat d am in new butsurface-treating, or sealing age; rv any other type of wax agent n h ar ula -1 2 mm. gfilhe 9 os i .ma be uti i s -adve ese Cqlqrin 1 pounds and other materials are contemplated as additives to our coating and lamination wax composition, whose 9 properties other than coating and laminating characteristics may be modified in any useful way by the addition of such substances.

We claim:

1. A microcrystalline hydrocarbon wax composition of high laminating strength and low-temperature flexibility consisting of approximately 85 parts by weight substantially oil-free microcrys'talline hydrocarbon wax having a melting point between 170 and 180 F. and approximately 15 parts by weight of an aromatic extract obtained by solvent extraction of mineral lubricating oil fractions, said composition having a laminating strength of at least 69 grams per inch and a flexibility at about -10 F. of at least 30 bends.

2. A composition in accordance with claim 1 in which the microcrystalline wax has a retained oil content below 1 percent by weight.

3. A composition in accordance with claim 2 in which the extract is obtained by phenol extraction of residual References Cited in the file of this patent UNITED STATES PATENTS 2,348,689 Abrams et al May 9, 1944 2,373,634 Wagner Apr. 10, 1945 2,441,202 Maier et a1. May 11, 1948 2,598,257 Hill et a1. May 27, 1952 

1. A MICROCRYSTALLINE HYDROCARBON WAX COMPOSITION OF HIGH LAMINATING STRENGTH AND LOW-TEMPERATURE FLEXIBILITY CONSISTING OF APPROXIMATELY 85 PARTS BY WEIGHT SUBSTANTIALLY OIL-FREE MICROCRYSTALLINE HYDROCARBON WAX HAVING A MELTING POINT BETWEEN 170 AND 180*F. AND APPROXIMATELY 15 PARTS BY WEIGHT OF AN AROMATIC EXTRACT OBTAINED BY SOLVENT EXTRACTION OF MINERAL LUBRICATING OIL FRACTIONS. SAID COMPOSITION HAVING A LAMINATING STRENGTH OF AT LEAST 69 GRAMS PER INCH AND A FLEXIBILITY AT ABOUT -10*F. OF AT LEAST 30 BENDS. 